This invention relates to reducing power usage in a personal computer.
In a laptop computer, for example, one scheme to lower power usage (to make the battery last longer before recharging) shuts off the display and the hard-drive motor and switches the microprocessor into a sleep mode if no key has been pressed for a preset time-out period, and turns them on again as soon as a key is next pressed. Additional power can be saved by having the keyboard control circuit operate only periodically, rather than continually, as it watches for a key to be pressed. If a key is pressed after the microprocessor has been asleep or the disk-drive motor has been off, there is a delay before the microprocessor or the disk drive is fully operable and the computer is again ready to interact with the user.